1. Field of the Invention
The invention belongs to the field of optical fiber communication, and more particularly to an optical add/drop multiplexer.
2. Description of the Related Art
Wavelength division multiplexing (WDM) is often used in optical fiber communication network to increase the information capacity for network transmission. In a WDM system, multiple signals are transmitted in the same communication path at different optical wavelengths, each wavelength is subjected to intensity modulation via different electric signals, and then, the modulated lights are combined into one communication path by an optical multiplexer, and at a receiver end, different wavelengths are separated by an optical demultiplexer and guided to different detectors.
The WDM system can be two types based on its channel quantity and spacing, i.e. coarse type and dense type. A coarse wavelength division multiplexing (CWDM) system has a smaller number of channels and larger wavelength spacing (usually 20 nanometers or more). A dense wavelength division multiplexing (DWDM) system a larger number of channels (more than 8) and small wavelength spacing, the common wavelength spacing is approximately from 0.2, 0.4 to 1.6 nanometers. DWDM is applied to high-level systems in communication hierarchy, however, it is more difficult and challenging to design than CWDM system.
The optical add/drop multiplexer (OADM) is an important routing apparatus used in communication network. An optical add/drop multiplexer can classify different wavelengths, separates and removes one wavelength component, and adds and inserts one new wavelength component, and all the wavelength components are combined into a single beam by the multiplexer. There are some problems in existing optical add/drop multiplexers, such as slow response, difficult to extend and high manufacturing cost, etc.